I teach Photoshop at universities and workshops. I have noticed a few things that could be improved to help people learn and use PS.

1. Many people have a hard time noticing when they have a Layer selected vs. it's Layer Mask. The thin Frame around these is not very prominent and all but disappears during projected lessons.

2. Panels tiny fly-out menu icons are hard to see and look insignificant, making most new users disregard it. My suggestion is to have a preference (under Interface) that allows for a user option that if chosen, lights up the thin frame around the Layer or it's Mask, when either is chosen. A yellow colored highlight would be optimal, just as is used in Lightroom 5's Level tool. Same for Panel Fly-out menus too. Here's a mockup of my basic idea: